1. Field of Invention
The present disclosure is to a method of wellbore logging, and more specifically is to using a pulsed neutron log to identify the presence of weighting material sag in a wellbore annulus, such as barite, hematite, and the like.
2. Description of Prior Art
Oil producing wellbores that intersect a subterranean formation are typically lined with a string of casing that is cemented to the formation. Sometimes inserted within the cemented casing string is an inner casing string. A producing well will generally include a string or production tubing that is set within the inner casing string, and through which fluid produced from the formation is directed to the surface. The production tubing is removable so that during the life of the well, various remediation, repair, or flow enhancement operations can be conducted within the well. Tubing is sometimes removed completely, such as prior to termination of production from and/or killing of a well.
The annular spaces formed between the casings and/or tubing usually becomes filled with drilling fluid. Drilling fluid usually include particulates, over time in the stagnant annulus the particulates can precipitate in the fluid and settle out to form hard deposits in the annulus. The hard deposits can span the radius of the annulus and adhere to the respective surfaces of the tubulars. When a sufficient amount of particulate deposits to concentric tubulars, they are effectively coupled to one another. In instances where the precipitate adheres to the tubing and surrounding casing, removing the tubing requires cutting the tubing. The step of cutting can be done with a cutting tool having a blade, a chemical cutter, or a flame. However, the cutting location must be carefully determined. If the cutting depth is below the adhesion, the tubing cannot be removed. Or if the cutting depth is too far above the adhesion, an extended section of free pipe may remain, which is also undesirable.